1. Field of the Invention
The present invention relates to a bending portion of an insertion part of an endoscope and an endoscope provided with the insertion part including such a bending portion.
2. Description of the Related Art
The endoscope comprises: an elongate insertion part having a proximal end and a distal end and adapted to be inserted into an inner space of an object with the proximal end of the insertion part being as a head; and an operation part connected with the proximal end of the insertion part to operate the insertion part. The insertion part includes an insertion part main body extending from the proximal end to a neighborhood of the distal end, a bending portion having an end connected to the extending end of the insertion part main body, and a tip portion having a base end connected to the other end of the bending portion.
In a case of a flexible endoscope, the insertion part main body is called as a flexible portion which can flex only in a radius larger than a radius of the flexible bending portion when the bending portion is bent.
In a case of a medical endoscope, an object into which the insertion part of the endoscope is inserted is a living thing and an inner space of the object is a body cavity of the living thing.
The bending portion includes a bending structure having a plurality of annular members interconnected by a plurality of connecting pins to be bendable as a whole in four directions (cross directions). In the bending structure, for example, peripheral walls of the adjoining annular members are connected with each other by two coaxial connecting pins extending in two opposite directions (right and left directions, for example), so that the two adjoining annular members can bent in two opposite directions (up and down directions, for example) perpendicular to the aforementioned two opposite directions. Then, other annular members further adjoining the two adjoining annular members have a peripheral wall connected with the peripheral walls of the two adjoining annular members by two coaxial connecting pins extending in two opposite directions (the up and down directions, for example) perpendicular to the aforementioned two directions (the right and left directions, for example), and therefore, can be bent in the aforementioned two directions (the right and left directions, for example) with respect to the two adjoining annular members.
Four operating wires extending from the operation part through the insertion part main body are inserted in each of the annular members of the bending structure of the bending portion, and the four operating wires are arranged at four positions equidistantly apart from each other in a peripheral direction in each of the annular members. The distal ends of the four operating wires are fixed to the annular member adjoining the tip portion. The two operating wires are distant from each other in the two directions (the right and left directions, for example) in each of the annular members, and the proximal ends of the two operating wires are coupled to a first bending portion operating lever (a bending portion right and left operating lever, for example) arranged on the operation part. The remaining two operating wires are distant from each other in the other two directions (the up and down directions, for example) perpendicular to the aforementioned two directions (the right and left directions, for example) in each of the annular members, and the proximal ends of the remaining two operating wires are coupled to a second bending portion operating lever (a bending portion up and down operating lever, for example) arranged on the operation part.
By operating the first bending portion operating lever (the bending portion right and left operating lever, for example) of the operation part, the bending portion together with the tip portion can bent in the two directions (the right and left directions, for example) at the extending end of the insertion part main body of the insertion part of the endoscope. Also, by operating the second bending portion operating lever (the bending portion up and down operating lever, for example), the bending portion together with the tip portion can bend in the remaining two directions (the up and down directions, for example) perpendicular to the aforementioned two directions (the right and left directions, for example) at the extending end of the insertion part main body of the insertion part of the endoscope.
Various electric/electronic parts including an imaging device are accommodated in an inner space of the tip portion, and conductive lines extend from these electric/electronic parts to the operation part through the bending structure of the bending portion and the insertion part main body.
Further, in the insertion part, light guide members extend from the tip portion to the operation part through the bending structure of the bending portion and the insertion part main body.
On a tip end surface of the tip portion, an objective lens group is mounted in liquid-tight manner to face the imaging device and light projecting lens are mounted in liquid-tight manner to face tip ends of the light guide members.
The bending structure of the bending portion is covered by a braid which in turn is covered by a liquid-tight flexible cover member. Conventional cover member is made of rubber.
The cover member has one end portion and an other end portion, the one end portion covering on a base end area of an outer peripheral surface of the tip portion, and the other end portion covering a distal end area of an outer peripheral surface of the insertion part main body.
The one and other end portions of the cover member are fixed in liquid-tight state to the base end area of the outer peripheral surface of the tip portion and the distal end area of the outer peripheral surface of the insertion part main body by tightly winding a thread member a number of times on each of the outer peripheral surfaces of the one and other end portions of the cover member.
A thermosetting adhesive for preventing is applied to the winding portion of the thread member on the outer peripheral surface of each of the one and other end portions of the cover member to prevent the winding portion of the thread member from loosening.
The aforementioned fixing structures at the both end portions of the cover member on the bending portion of the insertion part of the endoscope is widely known as disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication Nos. 2005-287575, 2000-166859 and 2004-166840.
Jpn. Pat. Appln. KOKAI Publication No. 2005-287575, for example, discloses an annular protrusion formed on an outer peripheral surface of one end portion of a cover member, and the annular protrusion is separated from one end surface of the one end portion. The annular protrusion clearly defines a range on which a thread member is tightly wound on the outer peripheral surface of the one end portion of the cover member after the one end portion of the cover member covers a coupling ring of an extending end of an insertion part main portion of an insertion part of an endoscope, to fix the one end portion of the cover member on the coupling ring in liquid-tight manner. At the same time, the annular protrusion prevents an adhesive which is applied to a winding portion of the thread member wound on the outer peripheral surface of the one end portion to prevent a loosening of the winding portion, from flowing out onto an outer peripheral surface of the remaining area of the cover member.
Jpn. Pat. Appln. KOKAI Publication No. 2000-166859 discloses that two end portions of the cover member are covered on an extending end area of an outer peripheral surface of an insertion part main body of an insertion part of an endoscope and on a base end area of an outer peripheral surface of an tip portion of the insertion part, and then thread members are wound tightly on the outer peripheral surfaces of the two end portions of the cover member to fix the two end portions of the cover member in liquid-tight manner on the extending end area of the outer peripheral surface of the insertion part main body of the insertion part and on the base end area of the outer peripheral surface of the tip portion of the insertion part, and then an adhesive is applied to the winding portion of the thread member on each of the both end portions of the cover member to prevent the winding portion from loosening, and finally a heat-shrinkable tube covers the adhesive.
Jpn. Pat. Appln. KOKAI Publication No. 2004-166840 discloses that two end portions of a cover member are covered on an extending end area on an outer peripheral surface of an insertion part main body of an insertion part of an endoscope and a base end area of an outer peripheral surface of a tip portion of the insertion part, and then thread members are wound tightly on the outer peripheral surfaces of the two end portions of the cover member to fix the two end portions of the cover member in liquid-tight manner on the extending end area of the outer peripheral surface of the insertion part main body of the insertion part and on the base end area of the outer peripheral surface of the tip portion of the insertion part, and finally an adhesive is applied to the winding portion of the thread member on each of the both end portions of the cover member to prevent the winding portion from loosening. The thread member is wound with a predetermined force on the outer peripheral surface of each of the two end portions of the cover member in such a manner that a thickness of each of the two end portions on which the thread members are wound is 40% to 95% of the thickness of each of the two end portions in a natural state in which the thread members are not wound on the two end portions.
In each of the conventional fixing structures for the both end portions of the cover member covering the bending portion of the insertion part of the endoscope, winding start and winding end portions of the thread member wound on the outer peripheral surface of each of the two end portions of the cover member are temporally fixed on each of the two end portions before applying the adhesive thereto as described below. Specifically, at first the winding start portion of the thread member is extended in a longitudinal direction of the cover member on each of the outer peripheral surfaces of the two end portions before the thread member is wound on each of the outer peripheral surfaces of the two end portions of the cover member, and the winding start portion of the thread member is pressed on each of the outer peripheral surfaces by winding the thread member on each of the outer peripheral surfaces of the two end portions. The winding end portion of the thread member is pulled in between the winding portion of the thread member formed on each of the outer peripheral surfaces of the two end portions of the cover member and each of the outer peripheral surfaces of the two end portions of the cover member, and thus extended in the longitudinal direction of the cover member.
Next, with reference to FIGS. 22 and 23, a typical example of the conventional fixing structure for fixing one end portion of the cover member on the base end area of the tip portion in the bending portion of the insertion part of the endoscope, will be explained.
A bending structure 2 of the bending portion 106 of the insertion part of the endoscope has a plurality of annular members 2a interconnected by a plurality of connecting pins 2b to be bendable as a whole for example in four directions (cross directions).
An intermediate portion of an outer peripheral surface of the bending structure 2 between the both end portions thereof is covered by a braid 10 knitted by thin metal wire or synthetic fiber into a tube.
In the bending structure 2 of the bending portion 106 of the insertion part of the endoscope, the other-end area including the other end connected to a base end of a tip portion 105 located at a position opposite to an extending end of an insertion part main body which is not shown, overlaps with a base-end area of the tip portion 105 including the base end thereof. The other end area of the bending structure 2 is fixed to the base-end area of the tip portion 105 by a plurality of fixing members 4. The conventional fixing member 4 is a headed screw.
The bending structure 2 of the bending portion 106 is covered by a flexible cover member 5 from not shown one end to the other end thereof. The conventional cover member 5 is formed of rubber. A thread member 6 is wound spirally on each of the outer peripheral surfaces of one and the other end portions of the cover member 5 and thus makes up a winding portion, the one end portion of the cover member 5 corresponding to the one-end area (overlapped with the extending end area of the not shown insertion part main body) of the bending structure 2, and the other end portion of the cover member 5 corresponding to the other end area (overlapped with the base end area of the tip end portion 3) of the bending structure 2.
Conventionally, the thread member 6 is wound on the outer peripheral surface of each of the one and other end portions of the cover member 5 in a manner described below.
At first, a portion of the thread member 6 in the neighborhood of a winding start portion 6b thereof is wound on each of the outer peripheral surfaces of the one and other end portions of the cover member 5 to form a knot 6a, and then the winding start portion 6b is extended along the longitudinal center line of the bending structure 2 on each of the outer peripheral surfaces. Next, the thread member 6 is spirally and tightly wound in a direction of an arrow in FIG. 22 on each of the outer peripheral surfaces to form a winding portion 6c and to make the winding start portion 6b is pressed on each of the outer peripheral surfaces by the winding portion 6c. A winding end portion 6d of the thread member 6 remaining after forming the winding portion 6c is pulled in between the winding portion 6c and each of the outer peripheral surface, so that the winding end portion 6d is temporarily fixed.
The winding start portion 6b of the thread member 6 and the winding end portion 6d thereof are extended substantially parallel to each other along the longitudinal center line of the bending structure 2 between each of the outer peripheral surfaces and the winding portion 6c. 
Each head 4a of the fixing members 4 fixing the other end area of the bending structure 2 to the base end area of the tip portion 105 while the other end area and the base end area are overlapping with each other generates an unevenness on the outer peripheral surface of the radially outer one of the other end area of the bending structure 2 and the base end area of the tip portion 105. As used herein, the term “radially side one” means one of i) the other end area of the bending structure 2 and ii) the base end area of the tip portion 105, the one being radially located outside of the other.
In FIGS. 22 and 23, the radially outer one is the other end area of the bending structure 2. After fixing the other end area of the bending structure 2 to the base end area of the tip portion 3, each head 4a of the fixing members 4 is machined to conform with the outer peripheral surface of the above described radially outer one. Nevertheless, it has been difficult to eliminate the unevenness completely.
The winding portion 6c of the thread member 6 is coated with a resin layer 6e of, for example, a thermosetting adhesive and covered by the resin layer 6e to prevent the winding portion 6c from loosening.
An endoscope used in a medical field must be sterilized after it is used. Various methods for sterilization are known. In a case where a sterilization method using an autoclave device is employed, a problem described below is liable to occur.
The endoscope to be sterilized is placed in the autoclave device and heated to a high temperature (about 135° C.) under high pressure by the autoclave device. In this time, the cover member 5 made of rubber is softened and decreased in its diameter.
In the case where the unevenness is generated on the outer peripheral surface of the radially outer one of the other end adjoining area of the bending structure 2 and the base end area of the tip portion 105 (in FIGS. 22 and 23, the radially outer one is the other end area of the bending structure 2), a change in stress distribution is generated at the boundary of the unevenness in the portion of the resin layer 6e corresponding to the unevenness through the cover member 5 during the sterilization using the autoclave device.
The thickness of a portion of the resin layer 6e corresponding to each of the winding start portion 6b and the winding end portion 6d of the thread member 6 wound on each outer peripheral surface of the one and other end portions of the cover member 5 is smaller than the thickness of the remaining portion of the resin layer 6e. 
In a case where at least one of the winding start portion 6b and the winding end portion 6d of the thread member 6 is overlapped with at least one of the heads 4a of the plural fixing member 4 as shown in FIGS. 22 and 23, therefore, the thin portion of the resin layer 6e (i.e. the portion of the resin layer 6e corresponding, through the cover member 5, to the aforementioned unevenness developed by the head 4a of the fixing members 4) corresponding to the at least one of the winding start portion 6b and the winding end portion 6d of the thread member 6 of the resin layer 6e is liable to crack due to the change in stress distribution caused by the remaining thick portion of the resin layer 6e during the sterilization using the autoclave device.
The cracking loosens the winding portion 6c of the thread member 6 wound on the cover member 5, and therefore, the liquid tightness provided by the cover member 5 may be disrupted.
FIGS. 22 and 23 further show light guide members 8 extending from the operation part not shown, through the bending structure 2 of the bending portion 106 and the insertion part main body not shown, to the tip portion 3. FIGS. 22 and 23 further show a plurality of conductive lines 9 extending to the operation part not shown, through the bending structure 2 and the insertion part main body not shown, from the various electric/electronic parts including the imaging device accommodated in the inner space of the tip portion 3.